Chances are improving that Congress will eventually give President Obama the vote he seeks to attack Syria. Leaders of both parties in the ever-contentious House signed on Tuesday, and most members seem likely to follow, if reluctantly.

And well they should. To repudiate such an unusual and unnecessary request would be an act of irresponsibility that would do immense damage, undercutting U.S. credibility, inviting trouble in both Syria and Iran, and potentially weakening future presidents.

All the same, it's astonishing that the nation finds itself in such a potentially embarrassing situation — put there by an ambivalent president who, like a novice chess player, made his early moves in Syria without anticipating the endgame.

Obama had the right instincts from the start — that the U.S. could neither entangle itself in Syria's intractable civil war, nor stand aside while the Syrian regime used chemical weapons. But he so thoroughly botched the strategy for reconciling those conflicting goals that when his "red line" on chemical weapons was conclusively crossed, he found himself isolated, vulnerable and in need of support.

It was an avoidable, unforced error, likely with enduring consequences.

But unlike President George H.W. Bush, who instantly declared that Saddam Hussein's 1990 invasion of Kuwait would not stand, Obama failed to ratchet up pressure, rally allies, build public support or involve Congress.

By April, the first reports of chemical attacks emerged. In June, when the intelligence community confirmed that the regime had killed 100 to 150 people in multiple strikes using the nerve agent sarin, the administration's response was muted.

In that context, the regime's monstrous Aug. 21 attack — which the Obama administration says killed 1,429 people, including hundreds of children — should have been no surprise. But so little groundwork had been laid that the British Parliament refused to endorse a retaliatory strike, other potential allies were unprepared and members of Congress began demanding a say, which Obama — with ships in place and all signs pointing to an imminent retaliation — abruptly granted.

A positive spin on the president's tactics is that once he realized his policy was in trouble, he stopped and retrenched. That's at least better than the impulsive hubris of the previous administration, which marched the nation into war in Iraq without understanding the consequences.

Obama could have attacked promptly, the most effective way to respond, then sought congressional approval for any follow-on action if Syrian President Bashar Assad repeated his offense. The delay gives the regime more time to move military assets out of the line of fire and civilians into it.

The larger lesson is about clear strategy and long-term preparation, both of which were absent. Obama, eager to draw support from Republican Sens. John McCain, Lindsay Graham and other hawks, is now talking about a comprehensive plan to support Syrian rebels and push Assad aside. Given the chaos in Syria, that stands to be a far more hazardous undertaking.

Assuming Congress gives Obama the green light he seeks, he had better think through the endgame before he makes his next move.

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